1. Field of the Invention
This invention relates to an absorbent article, such as a disposable diaper, an incontinence pad or a sanitary napkin, which is excellent in hygroscopicity (moisture absorbent property) and free from an uncomfortable feeling during use, such as stuffiness or stickiness, and to a method for controlling the humidity and the rise of the humidity in the area of the absorbent article during wear.
2. Description of the Prior Art
In a well-known manner, an absorbent article comprises a liquid permeable surface material, a liquid impermeable antileakage material and an absorbent member interposed therebetween for absorbing and retaining the liquid. The functions required of the absorbent article are to absorb excreted body fluid quickly and to prevent the return of the absorbed body fluid. Up to now, a variety of proposals, centered about these functions, has been made.
Recently, there has also been a demand for various functions concerning the feeling of the absorbent article during use. For example, it is strongly desired that the color of the body fluid diffused into the absorbent member be concealed and that the surface of the absorbent article in direct contact with the user's skin be similar to a cloth in both appearance and touch, and soft in feeling. As for feeling, inter alia, it has become a crucial task to reduce the stuffiness and stickiness of the absorbent article worn by the user.
The absorbent article is used in such a manner that it is in contact with a particular portion of the user's body for a prolonged period of time. In accordance with the improved absorbent performance of the absorbent article in recent years, the article tends to be used for prolonged period of time, so that the need to reduce stuffiness and stickiness is more strongly felt, than the need for improved feeling. That is, if the article is not improved with respect to stuffiness and stickiness, the skin in contact with the absorbent article is subjected to thermal stress for a prolonged period of time, and undergoes bloating under high humidity, such that, in the worst case, skin troubles, such as itching or a rash are produced to the extent that the user cannot continue to wear the absorbent article.
There has also been proposed a variety of techniques of improving a topsheet as a method for combatting the stuffy or sticky feel. For example, there has been proposed a technique of employing a non-woven fabric of an agglomerated mass of hydrophobic fine fibers, as a surface material for the topsheet, for creating a hydrophobic space between the body surface and the absorbent article, thereby improving the fluid retention property without impairing liquid permeability (Japanese Patent Laid-open Publication No. 58-180602). There has also been proposed a technique of improving the fluid retention property of the absorbent article by using a hydrophobic sheet, more specifically a film, having apertures, as a surface material for the topsheet (Japanese Utility Model Laid-open Publications Nos. 54-124398, 57-1340 and 61-45753). In sum, these prior-art techniques combat the stuffiness and stickiness by improving the fluid retention property, by preventing the body fluid absorbed into the absorbent article from seeping into the space between the topsheet and the skin in order to diminish the opportunity for body fluid to come into direct contact with the skin.
However, it is only possible with the above-described prior-art techniques to reduce the opportunity for body fluid to come into direct contact with the skin. That is, the prior-art techniques do not prevent the moisture taken up by the absorbent article from being vaporized under body temperature and dissipated towards the skin or do not remove the moisture transpired from the skin as vapor. Even granting that the liquid retention properties of the above-described prior-art techniques could be raised to the maximum so that the liquid return could be reduced substantially to zero, it is essentially impossible to eliminate the stuffiness or stickiness inherent in the absorbent article.